The present invention relates to a golf ball having its surface covered with a top coat layer of clear coating material. More particularly, the present invention relates to a golf ball having a top coat layer which remains clear and glossy and retains good coating performance for a long period of time.
Golf balls usually have a white enamel coating and a clear top coating, which give a clear, glossy surface for their good appearance.
Recently, golf balls without white enamel coating are spreading to meet requirements for their simplified manufacturing process. As a result, the top coat layer of clear coating material is required to be more uniform than before. Unfortunately, it is possible to form uniform coating film on the surface of golf balls but it is impossible to prevent the coating film from fading with time, so long as the coating material contains a conventional extender pigment such as silica and calcium carbonate.
The clear coating material tends to become poor in clarity because of the clay-based anti-sagging agent added thereto which is usually a natural product containing considerable impurities (although an artificial one is available in small quantities). On the other hand, wax-based anti-sagging agents are likely to adversely affect the properties and adhesion of the coating film.
U.S. Pat. No. 5,766,097 and U.S. Pat. No. 5,967,906 disclose a golf ball having a plurality of dimples on its surface coated with a top coat of urethane coating material and/or epoxy coating material which is incorporated with silica, clay, or calcium carbonate having a particle diameter no larger than 20 μm, preferably no larger then 10 μm.
However, even the golf ball mentioned above does not have a good appearance because of the unsatisfactory clarity and gloss of the coating film.